Conventionally, a configuration has been proposed where, as in Patent Document 1 (JP-A No. 2001-74283), an indoor unit of an air conditioner having a refrigerant circuit through which a combustible refrigerant circulates, a ventilation fan (a ventilation unit), and a sensor (a refrigerant leak sensor) that detects combustible gas are installed in a room (a target space), and when leakage of the combustible refrigerant has been detected, the ventilation unit is operated to thereby discharge the combustible refrigerant from the target space.